The invention relates to a semiconductor device including an electroluminescent diode having a narrow spectral range, which comprises a monocrystalline substrate consisting of a compound of elements of the columns III and V of the Periodical System according to Mendeleev of a first conductivity type, and an epitaxial layer on this substrate and also consisting of a III-V compound and of the first conductivity type, which epitaxial layer comprises an electroluminescent pn-junction.
The invention further relates to a method of manufacturing this device.
Such a device is generally known from the published British Patent Application GB-A-No. 2070859, now British Patent No. 2,070,859, corresponding to U.S. Pat. No. 4,414,558.
Due to its very favorable properties--especially stability and quantum efficiency--, Ga.sub.1-x Al.sub.x As is the most suitable material for the manufacture of light-emitting diodes having a very high efficiency in the visible red or infrared.
However, when considering the radiation spectrum of a Ga.sub.1-x Al.sub.x As layer deposited on a GaAs substrate by means of epitaxy from the liquid phase, it is found that the maximum luminous intensity lies in the proximity of a wavelength of 800 nm, but that there exists a parasitic radiation, whose wavelength lies in the proximity of 900 nm.
In telecommunication systems comprising optical fibers, in which use is made of electroluminescent diodes and wavelength multiplexing it is necessary that the signals emitted by light sources at closely-adjacent frequencies have a narrow spectral range so that these frequencies don't overlap each other.
It stands to reason that due to the occurrence of parasitic radiation in the proximity of 900 nm in the diodes obtained from Ga.sub.1-x Al.sub.x As, these diodes become practically unusable. It can be derived from experiments carried out with the diodes by the Applicant that the parasitic radiation is probably due to the luminescent properties of the GaAs substrate, the occurrence of this luminescence being due to reactivation, which is caused by the photons which are emitted by the diodes themselves during their operation. This phenomenon found in electroluminescent Ga.sub.1-x Al.sub.x As/GaAs diodes can also occur in other diode types, which are made of different III-V compounds and in which the substrate is activated by the operation of the diodes, while the parasitic radiation then has a different wavelength.